The methods and devices mentioned particularly relate to prototyping and mould-making, in which moulds and particularly swages are to be produced which are comparatively small and have to be produced with high accuracy.
In case of the method for producing a swage by means of a laser beam a laser beam is guided along the accessible work surface of a workpiece in the accessible work area in accordance with digitally stored shape data. This may, for example, be effected in a meandering or hatching manner. The laser power and other parameters are set so that the impinging laser beam partly evaporates the material at the position of incident so that it is removed from the surface. In this way the laser can, under an appropriate control, remove layers of material from the surface so that gradually a swage is produced. The guidance of a laser and the adjustment or control of the other parameters of the process is carried out with reference to the digitally stored data.
FIG. 1A is a schematic view of the above procedures. 11 designates a workpiece shown in cross section. 12 schematically indicates the laser beam emitted by a laser head 13. 17 schematically indicates the position of incident of the laser beam on the current bottom of the swage. 18 schematically indicates the individual layers which have already been removed. 19 indicates the desired final shape of the swage in broken lines. 20 indicates the current bottom of the swage, i.e. the presently exposed surface of the swage. 15 designates the side walls of the swage. The illustration of FIG. 1A is so that the side wall 15 and the swage bottom 20 can be well distinguished due to their angular correlation. This need not always be the case. Within the framework of the present application the term side wall generally identifies an accessible surface inside the swage positioned closer to the laser head 13 than the swage bottom 20 in its z-coordinate. 14 designates the workpiece table. Further FIG. 1A shows the used coordinate definitions. The plane of the drawing is the x-z-plane. The y-coordinate is perpendicular to it (and indicated diagonally). The work window 10 of the laser beam is therefore located in the x-y-plane.
FIG. 1B shows the conditions which may develop on the side walls during the removal of material by means of a laser beam in an enlarged scale. The laser beam 12 which is conic due to its focus is guided over the swage bottom 20 in the direction of the arrow 21. The evaporated, molten and sprayed material, particularly metal, is symbolised by the “jets” 23. Particularly the sprayed material is partly deposited in the swage again. Such re-deposited material is designated by the numerals 16 (the deposit on the side wall 15) and 22 (the deposit on the swage bottom 20). Deposits 22 on the swage bottom 20 are generally harmless since they are worked over during the next passage of the laser, and in particular they are removed in a controlled manner if a depth control is carried out. This does not apply to the deposits on the side wall 15. Since the side walls are not a priori worked over by the laser beam the deposits 16 remain on the side wall. In addition, they tend to grow: The material is sprayed up to a first, incidentally formed deposit from below (from the swage bottom 20) and is deposited there. The deposit thus grows in the direction towards the swage bottom 20. It also grows in the direction towards the inside of the swage as well as in the circumferential direction of the swage. The deposit then resembles a heap cone. Such deposits may significantly deteriorate the quality of the produced swage.